Originally Posted by
rpenmanparker
I've never seen or heard of this either. I would agree that proper preload is paramount. You could try carbon assembly paste on the steerer under the stem inner surface. That might keep things snug. Also make sure you have all the required small parts of the headset in the stack and in the right order. You may have botched the assembly of the parts.
I would never use carbon paste between a stem steerer clamp and steerer...for one...the paste could wick down into the top bearing past the top dust cover.
Yes, OP...check your bearing order...make sure you don't have one bearing upside down...angular contact bearings don't like that and will spoil the headset performance.